Chlorinated machine dishwashing composition and process

ABSTRACT

A chlorinated machine dishwashing composition is disclosed which includes a combination of an organic chlorinating agent and an alkali metal tripolyphosphate. Particles of the combination are coated or encapsulated with tetrapotassium pyrophosphate. An admixture of the coated combination with a low-foaming surfactant and a defoamer remains stable after long storage periods with respect to retention of both available chlorine and low-foaming characteristics during use even in the presence of proteinaceous substances. Cooking and eating utensils may be cleaned by a lowfoaming aqueous solution of the present machine dishwashing composition with less spotting and greater clarity than is generally experienced when using related compositions including chlorinated materials.

United States Patent Brennan et al. 1 Jan. 25, 1972 1 CHLORINATED MACHINE 3,306,858 2/1967 Oberle ..2s2/99 DISHWASHING COM OSITION AND 3,354,090 1 1/1967 Keast ..252/99 PROCESS Primary Examiner-Mayer Weinblatt [72] Inventors: William R. Brennan; Philip M. Sabatelli, AttorneyEugene M. Bond and Kenneth E. Prince both of Cincinnati, Ohio [73] Assignee: W. R. Grace 8: Co., New York, NY. [57] ABSTRACT A chlorinated machine dishwashing composition is disclosed [22] Flled: 1970 which includes a combination of an organic chlorinating agent [2 [1 App]. No.: 10,292 and an alkali metal tripolyphosphate. Particles of the combination are coated or encapsulated with tetrapotassium pyrophosphate. An admixture of the coated combination with [52] US. Cl. ..252/99, 1 17/100 A, 1 17/100 B, a ]0w foaming Surfactant and a defoamer remains stable after 252/96 252/187 252/316 long storage periods with respect to retention of both available [51] Int. Cl. ..Cl1d 7/56 chlorine and low foaming characteristics during use even in [58] Field of Search ..252/99, 96, 187, 316, 317; the presence of protcinaceous Substances Cooking and eating 117/100 100 B utensils may be cleaned by a low-foaming aqueous solution of the present machine dishwashing composition with less References Cited spotting and greater clarity than is generally experienced UNITED STATES PATENTS lvllsien using related compositions including chlorinated materi- 3,120,378 2/1964 Lee et a1. ..252/ 99 X 3 Claims, No Drawings CIILORINATED MACHINE DISHWASIIIN COMPOSITION AND PROCESS This invention relates to a detergent composition including an encapsulated combination of an organic chlorinating agent and an alkali metal tripolyphosphate, and to a method for preparing same. The present composition and method provide improved stability with respect to available chlorine and im proved defoamer stability. The composition is eminently suited for machine dishwashing even in the presence of proteinaceous substances.

The effectiveness of a solution of any given detergent composition used to perform a washing operation will vary with several factors such as concentration of the detergent, temperature of the washing solution, the nature of the soil being removed, the nature and amount of active detergent ingredients in the solution, hardness of the water and the like. One important consideration, however, for chlorinated detergents is stability with respect to available chlorine during storage. Typically, detergent compositions having chlorinating materials as components thereof experience degrading during storage with a resultant decrease in both available chlorine and general cleaning effectiveness.

Detergent compositions containing organic chlorinating agents and alkali metal phosphates are known to the an. One example of such a composition is that revealed by Keast in U.S. Pat. No. 3,354,090. Keast teaches a process for obtaining a mixture of an alkali metal dichloroisocyanurate and a hydratable salt, wherein an alkali metal dichloroisocyanurate is produced by reacting trichloroisocyanuric acid with an alkali metal cyanurate. A hydratable salt, such as an alkali metal phosphate, is added to the reaction mixture to obtain a desired water content in the resulting final mixture. Keast discloses the prepared composition to be useful in cleaning, disinfecting and bleaching applications, particularly in household cleaners or for incorporating in detergent blends used in home laundermg.

Alkali metal tripolyphosphates such as sodium tripolyphosphate are also commonly used as inexpensivebuilders in cleaning compounds to assist the detergent action and to inactivate the hardness of water in which the cleaner is used.

The desirability of a nondeteriorating detergent composition including an organic chlorinating agent and a low-foaming surfactant or defoamer has been long felt in the art. A major obstacle in developing such a composition has been storage degradation of conventional surfactants and defoamers by chlorinating agents desirably included in these detergents.

Oberle US. Pat. No. 3,306,858 teaches formation of a storage-stable detergent composition by a process which includes the step of agitating a mixture of a liquid organic nonionic surface active agent and a solid carrier material such as tetrasodium pyrophosphate or trisodium phosphate to absorb the surface active agent thereon. Thereafter the absorbed combination is spray coated with an aqueous phosphate solution, while agitating the ingredients, to encapsulate the absorbed combination including a surface active agent. At this point Oberle dries the encapsulated composition which is thereafter mixed with a chlorine releasing agent and other detergent constituents, if desired.

The prior art compositions containing an organic chlorinating agent have been found subject to several difiiculties. These detergent compositions, which are usually stored for long periods of time between manufacture and use, have been found to deteriorate with regard to those components contributing to defoaming capability and to release available chlorine prior to cleaning articles therewith. The prior art compositions have failed to provide a stable dishwashing detergent composition which is composed of an organic chlorinating agent combined with a defoaming agent and which is prepared by an efficient and relatively simple method.

Although US. Pat. No. 3,306,858 to Oberle substantially develops the state of the art regarding storage preservation of desired defoaming characteristics, it fails to provide substantial protection of the chlorinating agent. During extended storage, compositions prepared by the Oberle process are subject to a loss of chlorinating power particularly in very warm or humid atmospheres.

Accordingly, it has now been found that by the practice of the present invention, unexpected stability is displayed by a detergent composition prepared by a method which includes the steps of mixing an alkali metal tripolyphosphate with an organic chlorinating agent; thereafter coating particles of this mixture with tetrapotassium pyrophosphate; and subsequently forming an admixture of the coated chlorinating agenttripolyphosphate combination with a low-foaming surfactant, a high-molecular weight polyalkylene glycol and other constituents conventionally included in dishwashing detergent compositions, if desired. The present invention thus provides a machine dishwashing composition which effectively removes food soils from glassware, dishes and the like, in a manner characterized by greater clarity and freedom from spotting, while providing high stability of a chlorine release agent during storage and low-foaming characteristics during use.

Generally stated, the machine dishwashing composition of this invention includes from about 0.5 to about 8 parts by weight of an organic chlorinating agent combined with about 5 to about 60 parts by weight of an alkali metal tripolyphosphate. The composition further includes from about 2 to about 10 parts by weight of an alkali metal pyrophosphate as a coating for particles of the chlorinating agenttripolyphosphate combination.

The present composition may be prepared by first forming a mixture of an organic chlorinating substance with an alkali metal tripolyphosphate by any suitable mixing means. Thereafter, particles of this mixture are sealed or encapsulated by a protective coating of tetrapotassium pyrophosphate which effectively serves as a stabilizer for the encapsulated mixture. The encapsulated particles may then be directly and usefully blended with almost any desired detergent additives conventionally employed in machine dishwashing compositions without affecting the stability of the mixture which forms the core of the encapsulated particles.

The process of the present invention for preparing a chlorinated detergent composition which is stable with respect to available chlorine generally includes the steps of mixing an organic chlorinating agent with an alkali metal tripolyphosphate and thereafter coating or encapsulating particles of the mixture with an aqueous solution of tetrapotassium pyrophosphate. More particularly, the process includes mixing an anhydrous alkali metal tripolyphosphate with an organic chlorinating agent, and thereafter coating particles of the mixture by pouring or spraying onto the particles an aqueous solution, preferably concentrated, of tetrapotassium pyrophosphate. The encapsulated particles may directly thereafter by usefully combined, if desired, with other ingredients conventionally included in dishwashing detergent compositions such as water softeners, defoamers, builders, surfactants and the like, including materials which may otherwise react with the organic chlorinating agent. Because the organic chlorinating agent of the present invention is encapsulated, it does not readily react with other materials such as defoamers and surfactants.

The encapsulated portion of the present composition may be seasoned or aged before being mixed into a final product, or may be immediately incorporated into the final composition as desired. Aging is generally preferred to minimize an opportunity for chlorine in any unentirely encapsulated particles to adversely affect the composition. It is found that aging the encapsulated particles for periods of about 1 hour to about 3 days is ordinarily sufficient for any particles which are only partially encapsulated to decompose or release available chlorine. By thus aging the encapsulated particles, chlorine is deterred from reacting with materials such as defoamers or surfactants which are subsequently added in one embodiment of this invention.

Chlorinating agents found especially useful herein include alkali metal dichloroisocyanurates such as sodium and potassium dichloroisocyanurates. Other known chlorinating agents may also prove useful.

In addition to a chlorinating agent, the mixture of the present composition forming the core to be encapsulated contains as an essential ingredient a hydratable salt. Although the hydratable salt is preferably sodium tripolyphosphate, it may be any hydratable phosphate salt, for example, tetrasodium pyrophosphate, trisodium phosphate and others. The mixture to be encapsulated may also contain various other constituents conventionally employed in dishwashing detergent compositions including soluble alkali metal silicates such as sodium silicates having a Na O to SiO molar ratio of 1:1 to 123.6, and preferably, 1:1 to 1:3.5 or the corresponding potassium silicates. In addition, water soluble alkali metal borates such as calcined sodium tetraborate or borax or the water soluble alkali metal carbonates or bicarbonates such as sodium or potassium carbonates may be included. If the above constituents or various other useful diluents, builders, water softeners, ehelating agents, organic detergents, bactericides and the like are desired in the final composition, they may be included in the encapsulated core, but they are preferably admixed with the pyrophosphate coated core consisting essentially of an organic chlorinating agent and a tripolyphosphate. Necessarily excluded from the encapsulated portion of the present composition are those surfactants, defoamers, and other constituents which are degradable by the chlorinating agent included herein.

Surfactants used herein are preferably nonionic and low foaming. A preferred class includes linear alcohol alkoxylates such as, for example, ethanol methoxylate, methanol ethoxylate, n-butanol ethoxylate and the like.

Defoamers for use herein are preferably selected from the polyalkylene glycol class. A preferred defoamer is polyethylene glycol having a molecular weight from about 3,000 to about 10,000. Another preferred defoamer is polypropylene glycol in a similar molecular weight range.

The present composition may be used by forming an aqueous solution containing from about 0.05 to about 1.0 part by weight and preferably from about 0.05 to about 0.5 part by weight of the present dishwashing composition. The solution is desirably used at a temperature of from about 140 F. to about 200 F., and preferably from about 140 F. to about 160 F. This cleaning solution may be applied by any suitable means to the surfaces of articles to be cleaned. The present dishwashing composition is highly effective when used in spray washing equipment of the type conventionally used in cleaning articles used for cooking and eating. Highly effective cleaning with low foaming is obtained in institutional dishwashing machines with aqueous solutions of the present composition. After the step of cleaning has been effected, the thus cleaned articles are desirably rinsed with water and thereafter allowed to dry.

The present dishwashing composition is highly effective in removing food soils and residues from dishes, glassware, and other cooking and eating utensils in conventional dishwashing machines. Food residues are effectively removed by the present composition, and the cleaned dishes, glassware, and the like exhibit less spotting and greater clarity than with conventional cleaning compositions having chlorinating components therein.

The encapsulated particles of the present machine dishwashing composition contain, as essential ingredients, the following components in amounts indicated:

Hydratable alkali metal 5-60 15-45 phosphate Coating: Alkali metal pyrophosphate 2-10 3-8 In one embodiment of this invention the following components in the amounts indicated are admixed with the previously encapsulated core of essential ingredients:

Approximate Parts by weight Operable Preferred Component Range Range Nonionic low-foaming surface- 0.1-5 0.1-3 active agent Defoamer 0.1-5 0.1-3

In another embodiment the following components are admixed with a previously encapsulated core, surface active agent and a defoamer, in amounts indicated:

Approximate Parts by weight Operable Preferred Component Range Range Sodium carbonate l-60 20-50 Tetrasodium pyrophosphate l-20 5-15 Sodium hydroxide 5-30 5-20 A preferred composition includes an admixture of the below-indicated components with a mixture of core in- The dishwashing detergent composition of this invention is characterized by superior retention of the available chlorine in the chlorinating agent. In the present composition embodiment which includes a defoaming agent there is substantially no chlorine degradation of the foam suppressant. These advantages are maintained even during prolonged storage of the composition of this invention.

The invention is further illustrated by the following nonlimiting examples:

EXAMPLE 1 An embodiment of the present composition having the following ingredients in amounts indicated is prepared by the procedure described subsequently:

Component Parts by weight Sodium dichloroisocyanurate 3.5 Sodium tripolyphosphate 15 Tetrapotassium pyrophosphate 7.5 (60% aqueous solution) Sodium carbonate 41.5

Ethanol ethoxylate l Polypropylene glycol 1 (Molecular weight 3,000) Tetrasodium pyrophosphate 10.5 Sodium hydroxide 20.0

The sodium tripolyphosphate is mixed with the sodium dichloroisocyanurate in a conventional solids blender. The resulting blend is transferred into a Waring Blender into which the tetrapotassium pyrophosphate solution is thereafter slowly poured with continuous mixing of the ingredients for several minutes. The other ingredients are sequentially added to the Waring Blender in the tabulated order, with the exception that the polypropylene glycol is added simultaneously with the ethanol ethoxylate as a previously prepared liquid blend.

Comparative testing of a sample of the initially prepared composition and a sample stored for months at 38 C. indicates good retention of available chlorine and excellent retention of defoaming action.

Squares of plate glass 4 inches on each edge are soiled with 1 gram of a soil containing 50 parts peanut butter, 25 parts hydrogenated vegetable oil, and 25 parts butter. A Hobart A.M. dishwashing machine having a 48-second wash cycle and a l2-second rinse cycle is used to test the detergency performance of this composition. The wash water contains 0.3 percent of an initially prepared sample of this dishwashing composition and has a temperature of 150 F. in the wash section. The rinse water has a temperature of 180 F. The water used is Cincinnati tap water having a hardness of 161.5 p.p.m. in the test a set of plates of glass are run through 8 cycles in the machine with a drying period of minutes allowed between cycles. After completion of the 8 cycles the initially solid test plates are generally found to have a clear and bright appearance and notable freedom from spotting.

EXAMPLE 2 An embodiment of the present composition having the following ingredients in amounts indicated is prepared by the procedure of example 1:

Component Parts by weight Sodium dichloroisocyanurate 3.5 Sodium tripolyphosphate l5 Tctrapotassium pyrophosphate 7.5 (60% aqueous solution) Sodium carbonate 4L5 Ethanol ethoxylate l Polyethylene glycol I (molecular weight 6,000)

Tetrasodium pyrophosphate l0.5 Sodium hydroxide 200 The dishwashing test of example 1 is repeated for this composition, which is found to have essentially the same cleaning qualities as the example I composition. Testing as in example 1 shows this composition to be comparable to the example 1 composition with respect to retention of detergent effectiveness, available chlorine and defoaming action.

EXAMPLE 3 An embodiment of the present composition having the following ingredients in amounts indicated is prepared by the procedure of example 1:

EXAMPLE 4 An embodiment of the present composition having the following ingredients in amounts indicated is prepared by the procedure described subsequently:

Component Parts by weight Sodium dichloroisocyanurate Sodium tripolyphosphate Tetrapotassium pyrophosphate (60% aqueous solution) Sodium carbonate 45 Ethanol ethoxylate l Polypropylene glycol 1 (molecular weight 6,000) Tetrasodium pyrophosphate Sodium hydroxide Fine granules of sodium tripolyphosphate are mixed with granules of sodium dichloroisocyanurate in a conventional solids blender. Particles of this mixture are encapsulated by spraying the tetrapotassium pyrophosphate solution thereon with agitation of the particles. The coated mixture is aged for 6 hours during which the water solvent partly hydrates the sodium tripolyphosphate thereby rendering this portion essentially dry and solid.

A mixture of the other components is prepared by first spraying a liquid blend of the ethanol ethoxylate and the polypropylene glycol onto the sodium carbonate. Thereafter the tetrasodium pyrophosphate and the sodium hydroxide are sequentially added to the unencapsulated mixture while the mass is continuously agitated. The thus prepared unencapsulated portion of the composition is then admixed with the aged solid encapsulated portion in a ribbon blender for several minutes.

A sample of this composition, as initially prepared, is subjected to a dishwashing test as in example 1. The quality of cleaning is found to be even better than the example 1 composition. Testing of storage stability shows this composition to exceed the example 1 composition with respect to retention of available chlorine, defoaming action and detergency power.

EXAMPLE 5 The following components in amounts indicated are combined by the procedure described subsequently:

Component Parts by weight in a ribbon mixer are blended sodium carbonate and a previously prepared liquid mixture of ethanol ethoxylate and polypropylene glycol. To the resulting blend are sequentially added the other components with continuous agitation and in the order listed above. This method of preparation provides no encapsulation.

The thus formed composition is found to have a lower initial available chlorine content than the encapsulated compositions of examples 1 to 4, although the same amount of dichloroisocyanurate is included in all the examples. Upon storage this composition undergoes a significant loss of defoamer activity.

Typical defoamer stability and available chlorine retention test results are given below for the compositions of examples l, 4 and 5 which are prepared using encapsulation without aging, encapsulation with aging and no encapsulation, respectively.

Percent Foam height Example Available chlorine in inches Initial Stored Initial Stored l 2.41 1.97 56 V4" 4 2.24 2.16 V4 V4 5 2.02 2.0l V4 H4 Stored 4 months at 7080 F.

Stored 6 months at 70-80 F.

the aqueous mixture.

It is to be understood that the foregoing detailed description is given merely by way of illustration and that many variations may be made therein without departing from the spirit or scope of this invention.

We claim:

1. A process for preparing a dishwashing detergent composition which comprises combining from about 0.5 to about 8 parts by weight of sodium dichloroisocyanurate with about 5 to about 60 parts by weight of hydratable salt of sodium tripolyphosphate, coating particles of the resultant combination with from about 2 to about l0 parts by weight of tetrapotassium pyrophosphate, whereby particles of said combination of sodium dichloroisocyanurate and sodium tripolyphosphate are encapsulated with said tetrapotassium pyrophosphate.

2. The process of claim 1 wherein the prepared encapsulated particles are combined with from about 0.1 to about 5 parts by weight of a polyalkylene glycol, from about 0.] to about 5 parts by weight of a linear alcohol alkoxylate, from about I to about 60 parts by weight of sodium carbonate, from about 1 to about 20 parts by weight of tetrasodium pyrophosphate, and from about 5 to about 30 parts by weight of sodium hydroxide.

3. The process of claim 1 wherein the encapsulated core is aged from about 1 hour to about 3 days or more prior to admixing other components therewith. 

2. The process of claim 1 wherein the prepared encapsulated particles are combined with from about 0.1 to about 5 parts by weight of a polyalkylene glycol, from about 0.1 to about 5 parts by weight of a linear alcohol alkoxylate, from about 1 to about 60 parts by weight of sodium carbonate, from about 1 to about 20 parts by weight of tetrasodium pyrophosphate, and from about 5 to about 30 parts by weight of sodium hydroxide.
 3. The process of claim 1 wherein the encapsulated core is aged from about 1 hour to about 3 days or more prior to admixing other components therewith. 